Method of and apparatus for distributing pulverized fuel



Deb. 31, 1929. I w. DENISON I 1,741,184

METHOD OF AND APPARATUS FOR DISTRIBUTING PULVER IZED FUEL Filed NOV. 1 1925 2 Sheets-Sheet 1 Dec. 31, 1929.

G. W. DENISON METHOD OF AND APPARATUS FOR DISTRIBUTING PULVERIZED FUEL 2 Shuts-Shem. 2

Filed Nov. 1 1925 Patented Dec. 31, 1929 car srnrns PATENT OFFICE GEORGE W. DENISON, OF BAY VILLAGE, OHIO Application filed November 12, 1925.

This invention is concerned with fuel distributing systems for pulverized coal and the general object thereof is the provision of a system which will function to distribute the pulverized fuel in an air floated condition from a central source of supply to a plurality of burners in a uniform manner.

There are a number of coal pulverizing systems now in use embodying various man- 11ers of construction but which have in common, a coal pulverizing means from which extends a fuel conveying system in the form of atmospherically closed pipes through which the air floated fuel is driven by blowers. Some systems embody a direct fuel feed wherein fuel is driven through a single pipe from the crusher to the burner while others embody a circulating system wherein the air floated fuel is driven through a conduit or pipe from which extend branch pipes leading to the places of fuel consumption. This main pipe has a return stretch through which the fuel not dispensed through the branches returns to the main source of supply. In the 5 latter system the amount of air floated solid matter varies per cubic foot of air passing through each branch, and this is due to the fact that there has been no known means of preventing local circuits of fuel movement within the various parts of the system and whereby the solid matter or pulverized fuel becomes more dense in places.

A more specific object of my invention,

therefore, is the provision of a fuel distributing system which will distribute air floated fuel to each of a plurality of conduits or pipes extending to separate burners or places of consumption, in such a manner that a uniform density of the fuel conveying air may be maintained in the respective conduits when serviced from a central source of supply.

The objects of my invention also include the provision of a novel method of controlling the distribution of the powdered fuel carried by the fuel laden air to a plurality of ducts whereby each duct receives a uniform supply of powdered fuel.

Other objects of my invention will be hereinafter set forth in the following specifica- Serial No. 68,504.

tion which refers to the accompanying drawings illustrating a preferred embodiment thereof. The essential characteristics are summarized in the claims.

In the drawings Fig. 1 is an elevational diagrammatic view of a fuel pulverizing' plant embodying my invention; Fig. 2 is an enlarged vertical-section of an air density or fuel regulating means adaptable for use in a fuel conveying system such as is illustrated in Fig. 1; and Fig. 3 is a horizontal section just above the fan and through the discharge outlets.

In pulverized fuel burning systems, the fuel is usually dried to remove all the moisture therefrom, and is crushed or pulverized to the consistency of line flour and thereafter air floated by a blower associated with the pulverizer to the full carrying capacity of the air regardless of the amount of oxygen present per cubic foot of such conveying air. Such fuel laden air passes through bafiles whereupon the movement of the heavier particles of the fuel in the air, is interrupted and returned to the pulverizer. The fuel laden air is conducted to the place of consumption and there mixed with the proper amount of air to insure complete combustion of the air floated particles. If more than one burner or nozzle is to be serviced, branch lines are pro-' vided which extend from a main line. In such an installation considerable difficulty is encountered in that the velocity of the fuel laden air cannot be i'naintained uniform throughout the system, with the result that the air floated fuel precipitates or settles at various points in the system. Such accumulation or deposits of fuel results in ineflicient operation of the system, in that at least some of the nozzles are poorly serviced by the system. This difliculty also necessitates fur naces of a special construction.

My invention contemplates the provision of a mechanism which may be incorporated in such asystem in a convenient manner and which will function to distribute the fuel laden air to each one of several branch conduits leading to burners or nozzles whereby the fuel content of each cubic foot of air passing through each one of the conduits will be uniform and my apparatus comprises mechanism which by centrifugal action will distribute the fuel laden air from a central or main conduit to several nozzle conduits.

In the drawings in Fig. 1, I show at 10, a hopper or bin which is adapted to receive and store the fuel as it is dumped from a railroad car or from a preliminary crusher or grader. Disposed at the bottom of the hopper 10, is arranged a feeding apparatus in the form of a rotating disk 11, which moves the coal from the hopper 10 to a hopper 12 of a ball pulverizer 14, a stationary plate 13 serving to scrape the fuel into the hopper 12. The pulverizer 14 is enclosed and is connected to a conduit 15 extending upwardly to an adjustable vent 18. 7

Associated with a downwardly extending leg 16 of the conduit 15 is a motor driven .3 apparatus 20 which functions as a combined distributor and blower to draw the air floated fuel from the crusher 1 1 and to uniformly distribute the fuel to a plurality of ducts 30 leading to burners (not shown) disposed in a the fire boxes of a plurality of furnaces diagrammatically shown at 22.

The disposition of the fuel distributing apparatus 20, relative to the crusher 1 1 and the burners of the furnaces 22, is dependent upon the installing arrangementof the system for it is desirable that the fuel laden air be passed through the distributing apparatus without necessitating the passage thereof through a main duct, which is of any considerable length.

As shown in Figure 1, the distributing apparatus is spaced a sufficient distance from the end of the crusher 14, whereby the duct may extend upwardly to the vent 18 at a considerable angle relative to a horizontal plane, whereby the fuel may be drawn down in a vertical direction into the distributing apparatus in such manner as to prevent as much as possible uneven fuel density in the air entering the distributing apparatus and the character of this distributing apparatus is such as to overcome any remaining irregularities which may prevail in the fuel density of a column of air entering thereinto.

This distributing apparatus is also of such a character that while it functions as a blower it also serves to divide the fuel in the air passing through it uniformly to each of the fuel ducts 30 and 31. Such an apparatus is shown in cross section in Figure 2 and comprises a rotating bowl shaped member 3a suitably mounted upon the upper end of the armature shaft 35 of a motor 36. The motor as shown in Figure 1 may be suitably mounted on a base 38 at any desired elevation above the foundation level. The bowl 34 has formed about the perimeter thereof a flaring flange 39 which carries a plurality of radially extending fins or blades 10 and this portion of thebowl may constitute the blower of the fuel distributing system. The bowl may be enclosed at the top by a plate 15, having the under surfaces thereof fiat and disposed in juxtaposition to the radial blades of the blower portion of the bowl. The shape of this plate is such that it may be joined to a lower annular casing 46 which completes the blower housing.

Extending substantially tangential from the blower housing are a plurality of branches 48, shown in Figure 3, to which the ducts 3O anad 31 are attached. The shape of the passageways formed in these branches is such that the exit ends thereof are provided with circular discharge orifices 49, and the passageways as they extend inwardly toward the rotor are of such shape as to flatten and widen and meet each other and terminate immediately adjacent the perimeter of the blower portion of the bowl. The height of these passageways at the blower end are slightly greater than the dimension of the blower at the perimeter thereof. This lower casing member may be mounted on a suitable standard comprising upright members 50. Air diluting means may be incorporated into the distributing apparatus if desired and accordingly the under side of the flange 39 of the bowl may also be provided with blower plates 52 and a downwardly extending flanged opening may be provided to surround the bowl 34 and receive a vertically adjustable ring 5 1. This ring tends to obstruct the passageway adjacent the bowl which passage way furnishes inlet for the air drawn by the lower set of blower plates 52. As shown in Figure 2 this ring is mounted to slide within the casing flange 53 and rest upon adjustable screws 55. In the particular position illustrated this ring is adjusted to permit a small space 56 between the under side of the bowl and a beveled surface 53 of the ring. The uniformly distributed fuel laden air being forced into the ducts 30 and 31 may be thus diluted as desired. The particular adjusted position of the ring shows just sufficient passageway to permit the ingress of enough air to prevent the accumula tion of fuel dust within the blower housing beneath the blower flange and I prefer to rely upon the separate blower system 25, 26 for complete dilution of the fuel laden air but it is to be understood that is desired the distributing apparatus could function to be the only blower in the system from the pulverizing to the final combustion of the fuel.

The distributing apparatus embodies operative features in addition to those characteristics already described which are directed to an accurate control of the fuel in the air whereby it may be uniformly distributed to the several passageways of the system without interfering with the maintainance of a constant air flow through the system. It is to be understood that, in the foregoing described duct arrangement, the total crosssectional areas of the several ducts 30, 31 is substantially equal to the cross-sectional area of the main duct 15 and 16, so that theoretically there is no loss in velocity of the air being drawn through the main duct 15, 16 and forced through the several ducts 30, 31. To obtain the accurate distribution of the fuel being carried by the air passing through the system, the bowl 34 of the distributing apparatus is arranged to bear a certain relationship to the end of the duct 16 whereby the fuel may be precipitated out of the air into the bowl and redistributed to the respective ducts 30, 31 without obstructing the constant flow of the air through the system. I obtain this result by causing a local air velocity loss immediately above the bowl. Thus by arranging the end of the main duct 16, where it discharges into the bowl, to be adjustable relative to the bottom of the bowl and by contracting the end of the duct 16 in such a manner that it may be constructed to cause a local change in the velocity of the fuel laden air, the fuel will be precipitated into the bowl and this arrangement is such as to prevent the drifting of the fuel when it settles out due to the swirling'effect of the air.

As shown in Figure 2 the end of the duct 15 is extended into a member 60, comprising an adjustable continuation thereof and the member 60 is shaped somewhat after the manner of the duct of a Venturi meter to bring about the desired local pressure-velocity changes in the air. Member 60 as shown converges at 61 and is formed to be enlarged at 62 and con: tracted at the discharge end 63 thereof and is suitably mounted upon a cylindrical member 64 which is adjustably disposed on screw members 65 carried by the top member 45 of the blower housing. By adjusting the member 64 Vertically up or down relative to the bowl, it is possible to vary the pressure and velocity of the air when in the distributing apparatus environment.

Before setting forth in detail the operation of my apparatus the desired operating conditions for eiiicient pulverized fuel combustion will first be enumerated.

To maintain an efficient air conveying of a powdered fuel of the proper fineness, an air velocity of approximately 2000 feet per minute is required. Goal of the fineness to be floated at this velocity will comprise substantially one pound of coal in each 65 cubic feet of air, but such a fuel content at such a veloc ity constitutes an overcharge or overmix of powdered coal relative to the amount of oxygen required for complete combustion, for one pound of coal of the fineness above set forth will require approximately 225 cubic feet of air. It will thus be seen that the amount of additional oxygen required to obtain complete combustion is represented by the difierence between 225 cubic feet and 65 cubic feet of air. Practice, however, has demonstrated that if one pound of air floated fuel is drawn from the crusher per 100 feet of cubic air displaced therefrom, the fuel can be moved to the burners and the fuel laden air then diluted to 225 cubic feet per one pound of fuel. However, without the use of my apparatus a great many diiliculties arise in accomplishing this, some of which have been hereinbefore set forth. The foregoing requirements for a powdered fuel burning plant, should be borne in mind when considering the operation of my apparatus which is as follows:

Coal which has been screened or crushed to break up any large lumps present, is stored in the hopper 10. At the bottom of the hopper, as stated, is an opening to permit the fuel to be discharged upon the plate 11. The plate 11 isiconstantly rotated by a motor '70 through a shaft 71, chain and sprocket arrangement 72 and a gear transmission housed within a box 7 3 disposed beneath the plate 11. As the fuel drops to the plate 11 it is constantly removed there from by a stationary scraper plate 13, causing the coal to flow into the crusher hopper 14. The crusher hopper 12 may be rotated by a pinion 75 mounted on the shaft 71, the pinion meshing with a large gear suit ably mounted on the crusher. The fuel is pounded in the crusher by the constant agitation thereof and air is drawn from one end of the crusher to the other by entering at the opening of hopper 12 and then to duct 15 by action of the blower blades 40 of the distributing apparatus 20. The column of air being moved through the duct 15 has its velocity regulated by the manipulation of the vent 18 to approximate a velocity of 2000 cubic feet per minute and by regulating the rate of discharge of the hopper 10 to the crusher 14 and the speed of rotation of the latter, it is possible to charge the air leaving the duct 15 to the extent of one poundof fuel per 100 cubic feet of air. The air, thus heavily laden with powdered fuel will not carry the fuel in a uniform manner due to the swirling action thereof, and the column of air in the main duct accordingly does not carry a uniform amount of fuel throughout its cross section and particularly at its point of discharge into the bowl 341:.

The Venturi arrangement at the end of the duct 16 hereinbefore described, causes a decrease in the velocity of the air momentarily with a result that the fuel, by reason of its momentum, is discharged upon the bottom of the bowl 34. If the bowl were rotat-ed at a very slow speed the fuel would accumulate in ridges and drifts but the speed of the motor 36 is such as to immediately discharge this fuel in the form of minute ribbons of uniform thickness to the blower flange 39 and in this manner the fuel is divided up in uniform quantities to each of the passageways. If it is desired to dilute the fuel laden air whereby complete combustion of the fuel carried thereby may take place, this may be efiected by adjustment of the ring 53 relative to the bottom of the bowl. However, I have shown in the drawings, as already explained, an inclependent blower means for effecting final dilution of the fuel laden air at the burner nozzles.

It will be seen that by adjusting the end 63 of the member 60 comprising the end member of the conduit 15 and 16 of the distributing apparatus, the velocity of the air as it passes through thedistributing apparatus may be accurately regulated.

From the foregoing description of my invention it will be seen, that by my method of precipitating the air floated fuel out of the air drawn from the crusher and then redistributing the fuel while regulating the velocity of the air to a plurality of inde pendent ducts, I obtain a uniform fuel conuition in each of these ducts; also that complete combustion of the fuel is assured. An important advantage afforded by such a result is that the fuel may be burned in a furnace having a fire box of ordinary dimensions as distinguished from the prior practice of constructing powdered fuel burning furnaces with unusually long combustion chambers to obtain complete combustion of the fuel. The arrangement of my distributing apparatus is such that there are no surfaces on which the fuel can accumulate and interfere with the eflicient operation thereof and the entire apparatus is of such a simple character as to insure proper operation through long periods of constant use. In the use of my system the necessity for return fuel pipes is eliminated.

It should also be noted that if it is desired to vary the size of the fuel carrying pipes leading from the distributor to the burners this may be done by designing the branches extending from the perimeter of the rotary distributor so that the area of the branch entrance is substantially equal to the desired cross section of the fuel pipe. In this way it is practical to charge the fuel simultaneously into fuel pipes of different capacities While maintaining a uniform fuel density in all of the pipes.

I claim:

1. The method of distributing pulverized fuel to sources of consumption comprising establishing a stream of fuel laden air, causing a reduction in the velocity of said stream to consequently cause a precipitation of the fuel therefrom and dividing the moving air into a plurality of streams having substantially the same velocity as the original stream, the

streams being uniformly laden with fuel from the mass being continually precipitated.

2. The method of distributing pulverized fuel to sources of consumption comprising establishing a stream of fuel laden air, causing precipitation of the fuel out of the original stream while maintaining the continuity thereof and dividing the moving air into a plurality of streams while simultaneously redistributing the precipitated fuel to said streams uniformly.

3. In an apparatus of the character ,described, a source of fuel supply, a fuel precipitating chamber including a rotary member, a conduit for fuel laden air leading from the source of supply to the chamber, a plurality of fuel pipes leading from said chamber, said rotary member serving to distribute the fuel precipitated in the chamber uniformly to said fuel pipes, and said rotary member having a plurality of vanes serving as a blower for forcing the air from said conduit into said pipes, and adjustable means for controlling the velocity of the air.

4t. In an apparatus of the character described. a source of fuel supply, an enclosed fuel precipitatin chamber including a rotary member, a conduit for fuel laden air leading from the source of supply to the chamber, a plurality of fuel pipes leading from said chamber, said rotary member serving to distribute the fuel precipitated in the chamber uniformly to said fuel pipes, and said rotary member having a plurality of vanes serving as a blower for forcing the air from said conduit into said pipes. V

In an apparatus of the character de scribed, a source of fuel supply, an enclosed fuel precipitating chamber including a rotary member, a conduit for fuel laden air leading from the source of supply to the chamber, a plurality of fuel pipes leading from said chamber, said rotary member serving to distribute the fuel precipitated in the chamber uniformly to said fuel pipes.

6. In an apparatus for distributing pulverized fuel the combination of a large conduit, a plurality of smaller conduits, and means for distributing the fuel from the large conduit to the smaller conduits including a fuel precipitating chamber opening into the large conduit, and rotary means disposed within the fuel precipitating chamber for distributing the fuel to the smaller conduits.

In testimony whereof, I hereunto aflix my signature.

GEORGE W. DENISON. 

